Trends in dietary macronutrient composition and diet quality among US adults with diagnosed and undiagnosed elevated glycemic status: a serial cross-sectional study

Abstract

Background: Knowledge of glycemic status may affect dietary intake for subjects with diabetes and prediabetes.

Objectives: We aimed to determine whether trends of macronutrient intake and dietary quality differed by diagnosis of glycemic status among US adults with diabetes and prediabetes.

Methods: Data from NHANES 1999-2016 were analyzed. Diagnosed cases were established by self-report, and undiagnosed cases were defined by laboratory criteria (glycated hemoglobin ≥ 5.7%, fasting plasma glucose ≥ 100 mg/dL, or 2-h oral-glucose-tolerance test ≥ 140 mg/dL). A difference-in-differences model was used to compare the temporal trends between the 2 groups.

Results: There were 7502 diagnosed and 12,974 undiagnosed cases with elevated glycemic status included in the study. During 1999-2016, the intake of low-quality carbohydrates was lower, whereas intakes of high-quality carbohydrates, animal protein, plant protein, and unsaturated fat and the Healthy Eating Index 2015 (HEI-2015) score were higher, among the diagnosed cases than among the undiagnosed cases (P < 0.001 for all). However, in the trend analyses from 1999 to 2016, the increase in intake of high-quality carbohydrates was smaller among the diagnosed cases than among the undiagnosed cases (difference: -1.16%; 95% CI: -1.82%, -0.50%; P = 0.001). Moreover, the decrease in low-quality carbohydrate intake was smaller (difference: 0.79%; 95% CI: 0.01%, 1.57%; P = 0.05) and the increase in saturated fat intake was larger (difference: 0.44%; 95% CI: 0.08%, 0.79%; P = 0.02) among the diagnosed cases than among the undiagnosed cases. A significant difference of temporal trends in the HEI-2015 score between the diagnosed and undiagnosed cases was also observed, in favor of the undiagnosed cases (difference: -2.56; 95% CI: -3.71, -1.41; P < 0.001).

Conclusions: Although dietary habits among adults with diagnosed diabetes and prediabetes were better than those among the undiagnosed cases, these advantages have been diminishing during the past 2 decades.

Keywords: diabetes; diagnosed status; diet quality; difference-in-differences; macronutrient; prediabetes; trend.